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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Methyl acrylate is acutely toxic to freshwater algae.
EC50 (72 h, growth rate) = 3.55 mg/L (measured) (Selenastrum capricornutum, OECD TG 201)

Key value for chemical safety assessment

EC50 for freshwater algae:
3.55 mg/L

Additional information

An acute toxicity study was conducted withSelenastrum capricornutum (BAMM, 1995) according to OECD Guideline 201 using a static design. Nominal exposure concentrations were 0.60, 1.2, 2.4, 4.8, 9.5, 19, 38 mg/L. At time 0, the analyzed concentrations were 0.62, 1.3, 2.5, 4.2, 9.5, 19 and 34 mg/L. After 72 and 96 hours, analyses of the test media were all below the limit of quantification (LOQ) for the methodology (0.25 mg/L). Based upon the decline in test substance concentration over the 96-hour exposure period, the test results were presented based on 0-hour measured concentrations in the original report.

Thus, a recalculation of the more realistic effect values concerning growth rate was additionally performed taking the arithmetic means of the measured concentrations and the measured inhibition. Arithmetical means of the concentrations were 0.225, 0.325, 0.625, 1.5, 2.52, 4.75, and 12.08 mg methyl acrylate/L for the nominal concentrations of 0.60, 1.2, 2.4, 4.8, 9.5, 19 and 38 mg methyl acrylate/L. Missing 24 h measurements were considered to be 0 mg/L as worst case scenario. The recalculation provided 72 h-EC50 values for growth rate and biomass of 3.55 and 2.02 mg/L, respectively. These values indicate the toxicity of methyl acrylate to algae is similar to other aquatic species and the recalculated EC50 values were considered appropriate for the assessment.

 

In addition, there is an older study withScenedesmus subspicatus conducted according to Directive 87/302/EEC, part C.3 without analytical monitoring (BASF AG, 1989). EC50 values after 72 hrs exposure were recalculated and determined to be 18.3 mg/L (biomass) and 38.1 mg/L (growth rate), respectively. This study which does not take the possible decrease in test concentration by volatilisation of the substance into consideration and is therefore not suitable for the assessment.

 

In addition, a robust data set of acute studies is available from the other members of the acrylic ester category (2-ethylhexyl, ethyl, n-butyl, isobutyl, and tert-butyl acrylate).